Semiconductor Device comprising MIM-type Capacitor and Method of Manufacturing The Same
1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a semiconductor device which comprises an MIM (Metal Insulator Metal)-type capacitor using copper and a method of manufacturing the same.
2. Description of the Background Art
FIG. 94 is a cross section showing a structure of a semiconductor device comprising a capacitor in the background art. In an upper surface of a silicon substrate 101 formed is an isolation insulating film 102 made of a silicon oxide film. In an element formation region defined by the isolation insulating film 102, a MOS transistor is formed. The MOS transistor has a gate structure consisting of a gate oxide film 103, a gate electrode 104 and sidewalls 105 and source/drain regions 106 which are paired with each other with a channel region below the gate structure interposed therebetween. On the isolation insulating film 102 formed is a PIP (Polysilicon Insulator polysilicon)-type capacitor having a lower electrode 116 and an upper electrode 118 both of which are made of polysilicon and a dielectric film 117 of ON (Oxide Nitride) structure. The PIP-type capacitor can be formed with no additional complicate process since its upper electrode and lower electrode are each made of a polysilicon film which is widely used in a manufacturing process for a semiconductor device.
On the silicon substrate 101 formed is an interlayer insulating film 107 covering the MOS transistor and the PIP-type capacitor. In the interlayer insulating film 107 formed are a plurality of plugs 108 connected to the source/drain regions 106 of the MOS transistor and the upper electrode 118 and the lower electrode 116 of the PIP-type capacitor. On the interlayer insulating film 107, a first interconnection layer is formed. The first interconnection layer has an insulating film 109, a plurality of metal wires 110 formed in the insulating film 109 and a plurality of plugs 111 connected to the metal wires 110. The metal wires 110 are connected to the plugs 108, respectively.
On the first interconnection layer, a second interconnection layer is formed. The second interconnection layer has an insulating film 112, a plurality of metal wires 113 formed in the insulating film 112 and a plurality of plugs 114 connected to the metal wires 113. The metal wires 113 are connected to the plugs 111, respectively. On the second interconnection layer formed are a plurality of metal wires 115 connected to the plugs 114, respectively.
The PIP-type capacitor, however, whose voltage coefficient (VCC) is about 220 ppm/V and temperature coefficient (TCC) is about 120 ppm/xc2x0 C., which cause a relatively large variation in capacitance due to voltage variation and temperature variation, has a problem of unstable characteristics against voltage variation and temperature variation. Further, since the resistance value of polysilicon is relatively large, especially when the PIP-type capacitor is used for a radio frequency circuit, there arises a problem of low stability of circuit operation.
In an attempt to solve the problems of the PIP-type capacitor, recently, there has been a promotion of development of an MIM-type capacitor having an upper electrode and a lower electrode made of a metal. The MIM-type capacitor, whose VCC value is a fifth to a sixth of that of the PIP-type capacitor and TCC value is a half of that of the PIP-type capacitor or lower, has high stability of characteristics against voltage variation and temperature variation. Further, since a metal has lower resistance value than polysilicon, when the MIM-type capacitor is used for a radio frequency circuit, the stability of circuit operation is improved as compared with the case of using the PIP-type capacitor.
The MIM-type capacitor is formed together with the metal wires in a BEOL (Back End Of the Line) process which is one of the semiconductor manufacturing processes. In the background-art BEOL process, an aluminum wire is generally used as a metal wire. Since there has arisen a problem of wire delay in aluminum wire as devices have become smaller, however, a copper wire which has lower resistance than the aluminum wire has been recently being used. The copper wire is generally formed in a damascene process, not in an etching process, due to the difficulty of copper in patterning by etching unlike aluminum. Therefore, forming an MIM-type capacitor having copper electrodes needs a new structure and a new process, unlike the MIM-type capacitor having aluminum electrodes in the background art.
An object of the present invention is to provide a semiconductor device and a method of manufacturing the same, in which an MIM-type capacitor can be formed together with metal wires with no additional complicate process when the metal wires are formed by a damascene process step in the BEOL process.
According to a first aspect of the present invention, the semiconductor device includes a substrate, a semiconductor element, an interlayer insulating film, and an MIM (Metal Insulator Metal)-type capacitor. The semiconductor element is formed on the substrate. The interlayer insulating film is so formed on the substrate as to cover the semiconductor element. The capacitor is formed in the interlayer insulating film and electrically connected to the semiconductor element. The capacitor has a first metal film, a dielectric film, and a second metal film. The first metal film is formed on side surfaces and a bottom surface of a recess defined in the interlayer insulating film, serving as a first electrode. The dielectric film is formed on the first metal film. The second metal film fills the recess and is opposed to the first metal film with the dielectric film interposed therebetween, serving as a second electrode.
In this semiconductor device, the first electrode is formed not only on the bottom surface of the recess but also on the side surfaces thereof. Therefore, the area in which the first electrode and second electrode are opposed to each other is enlarged and the capacitor capacitance is thereby increased.
According to a second aspect of the present invention, the semiconductor device includes a substrate, a semiconductor element, an interlayer insulating film, and an MIM (Metal Insulator Metal)-type capacitor. The semiconductor element is formed on the substrate. The interlayer insulating film is so formed on the substrate as to cover the semiconductor element. The capacitor is formed in the interlayer insulating film and electrically connected to the semiconductor element. The interlayer insulating film has a predetermined insulating layer. The capacitor has a first metal film, a dielectric film, and a second metal film. The first metal film is formed in a main surface of the insulating layer, serving a first electrode. The dielectric film is formed on a side surface of the first metal film in the main surface of the insulating layer. The second metal film is opposed to the first metal film with the dielectric film interposed therebetween in the main surface of the insulating layer, serving as a second electrode.
In this semiconductor device, since the first electrode and the second electrode are formed in the same plane, the flatness of surface is improved as compared with the case where the first electrode and the second electrode are layered. Therefore, when the MIM-type capacitor is formed in the multi-level wire structure, it is possible to suppress level difference in the surfaces of interconnection layers.
According to a third aspect of the present invention, the semiconductor device includes a substrate, a semiconductor element, an interlayer insulating film, and an MIM (Metal Insulator Metal)-type capacitor. The semiconductor element is formed on the substrate. The interlayer insulating film is so formed on the substrate as to cover the semiconductor element. The capacitor is formed in the interlayer insulating film and electrically connected to the semiconductor element. The capacitor has a plurality of first metal films, a second metal film, a dielectric film, and a third metal film. The plurality of first metal films are connected to one another with a wire formed in the interlayer insulating film. The second metal film is formed extending onto the plurality of first metal films, serving as a first electrode together with the plurality of first metal films. The dielectric film is formed on the second metal film. The third metal film is opposed to the second metal film with the dielectric film interposed therebetween, serving as a second electrode.
In this semiconductor device, the dielectric film is formed not directly on the first metal films but on the second metal film. Therefore, a film other than the antioxidizing film for the first metal film can be used as the dielectric film.
Moreover, since the first metal film is divided into a plurality of films, the area of an upper surface of each divided first metal film is reduced. Therefore, it is possible to reduce dishing in the CMP process.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.